Decreased maximum mid-expiratory flow rate indicates obstruction in: (DNB Dec 2012)
|D||Trachea & Bronchi both|
FEF25 – 75% (MMEFR)- Average expiratory flow rate during middle 50% of the FVC. Also called maximal mid expiratory flow rate. It is regarded as a more sensitive measure of small airway narrowing than FEV1. In spirometry. It is effort independent.
With obstructive disease only in the small airways, the only abnormality noted on routine testing of pulmonary function may be a depression in FEF 25-75% and an abnormal terminal portion of forced expiratory flow volume curve. FEV1 /FVC may be normal.
Important Point about FEV 25% - 75%
1). Values between 80 – 120% of predicted values are normal.
2). Mild obstructive (small airway) diseases have decrease FEF25 – 75% with normal FEV1/FVC.
Other investigations is respiratory diseases
1). Radionuclide scans Q Ventilation/perfusion (V/Q) scans are used to diagnose pulmonary Q embolism.
2). Computed tomography
High resolution CT (HRCT) is used to diagnose
a. Interstitial lung disease
Spiral CT pulmonary angiography is used in the diagnosis of PE. It is the investigation of choice for screening of PE. (PNQ)
Note: Previously investigation of choice for screening of PE was V/Q scan.
Pulmonary angiography is also used for confirming diagnosing of PE and pulmonary hypertension Q.
3). Fiberoptic bronchoscopy.
a. Suspected lung carcinoma
b. Pneumonia in the immunosuppressed
c. Slowly resolving pneumonia
d. Interstitial lung disease
Aspiration of mucus plugs causing lobar collapse ii. Removal of foreign bodies.
4). Bronchoalveolar lavage (BAL) is performed at the time of bronchoscopy by instilling and aspirating a known volume of warmed, buffered 0.9% saline into the distal airway.
a. Suspected malignancy
b. Pneumonia in immunosuppressed (especially HIV)
c. Suspected TB (if sputum negative)
d. Interstitial lung diseases (eg sarcoidosis, extrinsic allergic alveolitis, histiocytosis)
Therapeutic indications: alveolar proteinosis.
1). Hypoxia (give supplemental O2)
2). Transient CXR shadow
3). Transient fever
4). Infection (rare).